Marlin with Sweet Potato Lime Risotto

Name: Marlin with Sweet Potato Lime Risotto
Ingredients: 2 tablespoons grapeseed oil; 1 large sweet onion (such as Vidalia), diced small; 1/2-ounce peeled fresh ginger root (1-inch piece), minced; 3 garlic cloves, lightly crushed with the side of a knife blade and minced; 4 to 6 sweet potatoes or 3 yams, peeled and cut in thin julienne then cut crosswise into 1/2-inch pieces); 1 firm mango, peeled and cut away from the seed; 1 quart coconut milk; 4 to 5 scallions, white and tender green parts only, sliced on the diagonal into 1/2-inch pieces; 1 fresh lime; 1 tablespoon grapeseed oil; 8 (6-ounce) marlin steaks, soaked in cold water if it is cured; Salt and freshly ground black pepper; 1 fresh lime, sliced for garnish